Since its debut, Lich King has continued to top the PC sales charts, with Blizzard today noting that the expansion sold over 4 million copies during its first month at retailers.

"The base World of Warcraft game and the World of Warcraft Battle Chest are performing better than last year," noted GameStop VP Bob McKenzie. "That type of traction is very impressive for a game that is going into its fifth holiday season and speaks to the enthusiastic player base Blizzard Entertainment products have."

World of Warcraft's Subscriber DefinitionWorld of Warcraft subscribers include individuals who have paid a subscription fee or have an active prepaid card to play World of Warcraft, as well as those who have purchased the game and are within their free month of access. Internet Game Room players who have accessed the game over the last thirty days are also counted as subscribers. The above definition excludes all players under free promotional subscriptions, expired or cancelled subscriptions, and expired prepaid cards. Subscribers in licensees' territories are defined along the same rules.